Electrostatic spraying of atomized material



Aug. 14, 1962 H.-HEUSCHKEL ELECTROSTATIC SPRAYING OF ATOMIZED MATERIAL Filed Dec. 9, 1960 INVENTOR. Hans He usc hke I BY Unite 3,049,301 ELECTROSTATIC SPRAYKNG OF ATOMIZED MATERIAL Hans Heuschkel, Wurttemberg, Germany, assignor to Escher Wyss G.m.b.H., Wurttemherg, Germany, a corporation of Germany Filed Dec. 9, 1960, Ser. No. 74,811 Claims priority, application Germany Dec. 18, 1959 3 Claims. (Cl. 239-15) Electrostatic spraying apparatus are known in which the materials to be sprayed are sprayed by electrostatic forces from blade-like spraying edges which are at a high electrical potential on to the object to be provided with a surface coating. In such cases, it is necessary that the material to be sprayed should not be electrically conductive. As is known, however, aqueous solutions, and electrically conductive material when it is sufficiently thinly liquid, can be atomized from. the liquid surface in the form of an extremely fine mist under the action of ultrasonic waves. This mist can then be electrically charged so as to be conducted to a counter-electrode under the influence of the electrostatic forces.

The invention relates to an electrostatic spraying apparatus for material atomized in the form of a mist, by means of which electrically conductive spraying material can be applied in layers to objects and foils just as well as non-conductive spraying material can be. applied thereto by means of the known apparatus.

The apparatus comprises for this purpose a spraying nozzle having an outlet aperture in the form of a gap for the mist of material to be sprayed and a cathode arranged in the spraying nozzle. The cathode is preferably constructed in the form of a broom in such manner that the individual wires of the broom-like cathode extend in spaced relationship through the center line of the crosssection of the gap-like outlet aperture of the nozzle in the longitudinal direction of the said aperture.

A constructional example of the subject of the invention is illustrated in simplified form in the drawings, in which:

FIGURE 1 is a longitudinal section through the apparatus and FIGURE 2 is a View from the outlet side.

The apparatus consists substantially of a housing 1, a nozzle 2 adjoining the upper side of the latter and a cathode 3 disposed in the said nozzle. The housing 1 is provided with an obliquely downward extending tubular branch 4 which issues from the lowermost part of the housing 1 and serves for the supply of the spraying material atomized in the form of a mist. The said tube is connected, for example, to an ultrasonic atomizer (not shown) for aqueous solutions or electrically conductive liquid spraying material.

The electrical voltage is applied to the cathode by means of a conductor 5 which extends through a plug 6 closing the lower end of the housing 1 and is surrounded by a tube 7 within the housing 1.

Owing to the high voltage app-lied to the cathode 3, the parts 1, 2, 4, 7 are preferably made of glass in order to guide the mist satisfactorily to the nozzle without being affected by the voltage.

The nozzle 2 has a gap-like outlet aperture 8. The cathode 3 is provided with a plurality of Wires 9 extending Patented Aug. 14, 1962 toward the outlet gap 8 of the nozzle 2 and imparting a broom-like form to the cathode. The wires 9 extend in spaced relationship through the center line of the crosssection of the gap-like aperture 8 in the longitudinal direction of the said aperture.

The mist of spraying material entering the tubular branch 4 first enters, under a light superatmospheric pressure, the housing 1 forming a fore-chamber. It then enters the nozzle 2 in a steady state and free from drops and flows past the broom-like electrode 3, 9 through the gaplike outlet aperture 8 into the atmosphere. The tips of the wires '9 impart an unipolar charge to the mist, so that it uniformly coats objects or foils which are at an opposite electrical potential.

The condensate separated from the mist in the form of drops in the fore-chamber 1 of the apparatus can flow back by gravity to the atomizer through the tubular branch 4 which at the same time serves for the supply of the mist of material to be sprayed.

What is claimed is:

1. Electrostatic spraying apparatus for spraying a mist of atomized material comprising a nozzle having an elongated gap as an outlet, a conduit for supplying mist to the gap and a chamber therebetween constituting a path of flow for the mist from the conduit to the gap; a broomshaped electrode disposed Within the path of flow, the electrode comprising a body and a plurality of laterallyspaced Wires extending therefrom in the direction of flow, said wires projecting through the gap and lying on its elongated centerline and means electrically insulated from the nozzle for applying an electric potential to the electrode.

2. Electrostatic spraying apparatus for spraying a mist of atomized material comprising a nozzle having an elongated gap as an outlet, a conduit for supplying mist to the gap and a chamber therebetween constituting a path of flow for the mist from the conduit to the gap; a broomshaped electrode disposed within the path of flow, the electrode comprising a body and a plurality of laterallyspaced wires extending therefrom in the direction of flow, said wires projecting through the gap and lying on its elongated centerline; means electrically insulated from the nozzle for applying an electric potential to the electrode and means for discharging from the chamber any liquid collected therein.

3. The apparatus defined in claim 2 wherein the liquid is collected by gravity in an end of the chamber remote from the gap and the body of the electrode, and the discharging means, comprises a tubular branch that discharges by gravity the liquid from that end of the chamber, the tubular branch constituting at least a portion of the mist supplying conduit.

References Cited in the file of this patent UNITED STATES PATENTS 1,854,475 Littlefield Apr. 19, 1932 2,571,608 Plagge Oct. 16, 1951 2,754,225 Gfeller July 10, 1956 2,766,064 Schweitzer Get. 9, 1956 2,826,513 Blanchard Mar. 11, 1958 2,890,388 Crosky et a1 June 9, 1959 2,901,178 Norris Aug. 25, 1959 

